Generate truth tables for boolean specs

[cjbrooks12]

Add a way to take a single Spek<T, Boolean> and flatten out all its sub-speks to build into a truth table.

Using the following snippet from the README:

val permissionSpek = HasExplicitCapabilitySpek("write")
        .or(IsRoleSpek("author").andNot(HasExplicitCapabilityRevokedSpek("write")))
        .or(IsSuperuserSpek())

should produce the following table

HasExplicitCapabilitySpek	IsRoleSpek	HasExplicitCapabilityRevokedSpek	IsSuperuserSpek	Result
false	false	false	false	false
false	false	false	true	true
false	false	true	false	false
false	false	true	true	true
false	true	false	false	true
false	true	false	true	true
false	true	true	false	false
false	true	true	true	true
true	false	false	false	true
true	false	false	true	true
true	false	true	false	true
true	false	true	true	true
true	true	false	false	true
true	true	false	true	true
true	true	true	false	true
true	true	true	true	true